Thermoplastic resin-coated ammonium polyphosphate and process for the preparation thereof

ABSTRACT

Thermoplastic resin-coated ammonium polyphosphate comprises a core material which comprises ammonium polyphosphate and a thermosetting resin, a melamine monomer or a surface-treating agent; and a coating layer of a thermoplastic resin which covers the core material. The thermoplastic resin-coated ammonium polyphosphate is excellent in water resistance, resistance to acids, resistance to alkalis, resistance to ions and resistance to organic solvents and if it is incorporated into a resin composition as a component of a flame retardant used therein and the composition is formed into a molded article, the resulting article does not show any marked reduction of its mechanical strength.

TECHNICAL FIELD

The present invention relates to thermoplastic resin-coated ammoniumpolyphosphate which comprises a core material comprising ammoniumpolyphosphate and, for instance, a thermosetting resin, a melaminemonomer or a surface-treating agent; and a particular thermoplasticresin covering the core material, a process for producing the coatedammonium polyphosphate and a flame retardant containing the same. Morespecifically, the present invention pertains to thermoplasticresin-coated ammonium polyphosphate which comprises a core materialobtained by encapsulating, modifying or surface-treating ammoniumpolyphosphate with, for instance, a thermosetting resin, a melaminemonomer or a surface-treating agent, or obtained by mixing ammoniumpolyphosphate with a melamine monomer; and a thermoplastic resinprepared by polymerizing a monomer having a plurality of specificfunctional groups and capable of undergoing two- or three-dimensionalcross-linking reaction, as well as a process for producing the coatedammonium polyphosphate and a flame retardant containing the same.

BACKGROUND ART

Heretofore, ammonium polyphosphate has been used and added to paper,wood, synthetic resins or the like as a component for a flame retardantused therein. However, ammonium polyphosphate is water-soluble by natureand therefore, has such characteristic properties that it is highlysusceptible to hydrolysis under a high temperature condition. A resincomposition in which such un-treated ammonium polyphosphate is blendedor an article obtained by molding the resin composition is also inferiorin water resistance due to the water-solubility of ammoniumpolyphosphate and is limited in the practical applications. Moreover,the un-treated ammonium polyphosphate is insufficient in the affinityfor synthetic resins and accordingly, the molded article obtained usinga resin composition to which the ammonium polyphosphate is added as acomponent for a flame retardant suffers from a problem in that themechanical strength, appearance or the like of the molded article arelargely impaired due to the presence of the polyphosphate.

To eliminate the drawbacks peculiar to the ammonium polyphosphate, therehave been some proposals. Ammonium polyphosphate which is subjected tocoating or encapsulation with a thermosetting resin is disclosed in, forinstance, U.S. Pat. Nos. 4,467,056, 4,347,334 and 4,514,328; JapaneseExamined Patent Publication (hereinafter referred to as “J.P. KOKOKU”)Nos. Hei 4-20944 and Hei 4-55625; and Japanese Un-Examined PatentPublication (hereinafter referred to as “J.P. KOKAI”) Nos. Sho 61-98719,Sho 61-98721, Sho 61-98722, Sho 61-101514, Hei 6-24719 and Hei 7-277713.In addition, ammonium polyphosphate which is treated, coated or modifiedwith a melamine monomer is disclosed in J.P. KOKOKU Nos. Sho 52-39930,Sho 53-15478 and Hei 5-50536; U.S. Pat. No. 4,515,632; and RegisteredJapanese Patent No. 2,598,742. J.P. KOKAI No. Hei 3-131508 and PCT No.9,208,758 disclose ammonium polyphosphate coated with a silicone resin.U.S. Pat. Nos. 5,071,901, 5,109,037, 5,162,418 and 5,164,437 discloseammonium polyphosphate which is treated with a surface-treating agent.

However, all of the ammonium polyphosphate products produced accordingto the processes disclosed in the aforementioned prior arts suffer fromproblems in that they are insufficient in the affinity for thermoplasticresins and dispersibility therein and that the articles obtained bymolding the compositions prepared by blending the products into resinshave considerably reduced mechanical strength. In order for eliminatingthese problems, a halogen-free flame retardant which is coated with orencapsulated in a thermoplastic resin has recently been proposed in J.P.KOKAI Nos. Hei 9-40876 and Hei 9-13037.

However, the halogen-free flame retardant which is coated with athermoplastic resin according to the process disclosed in these patentssuffers from problems in that it is still insufficient in the chemicalresistance such as acids, alkalis and organic solvents and that if thecore material comprises ammonium polyphosphate, the flame retardant isnot improved even in its water resistance.

The inventors of this invention have conducted various studies to obtainammonium polyphosphate which is excellent in water resistance,resistance to acids, resistance to alkalis, resistance to ions andresistance to organic solvents and which can provide an article whosemechanical strength is not impaired to a considerable extent, when acomposition is prepared by blending ammonium polyphosphate into athermoplastic resin as a component of a flame retardant used therein andthen molded into the article. As a result, the inventors have found outthat the foregoing problems can be solved by providing a substance whichcomprises a specific core material containing such ammoniumpolyphosphate and a thermoplastic resin coating the core material, inparticular, a coating layer of a thermoplastic resin consisting of across-linked polymer of a specific monomer having, in the molecule, 1 to5 groups each carrying polymerizable double bond and have completed thepresent invention on the basis of the foregoing finding.

As will be clear from the foregoing, an object of the present inventionis to provide a substance mainly comprising ammonium polyphosphate,which is excellent in water resistance and chemical resistance, whichcan provide an resin molded article whose mechanical strength is notimpaired to a considerable extent by blending ammonium polyphosphateinto a thermosetting or thermoplastic resin as a component of a flameretardant used therein and which has a high hygroscopicity-controllingeffect, as well as a process for producing the same and a flameretardant containing the same.

DISCLOSURE OF THE INVENTION

The thermoplastic resin-coated ammonium polyphosphate according to thepresent invention is characterized in that it comprises a core materialcomprising ammonium polyphosphate and, for instance, a thermosettingresin, a melamine monomer or a surface-treating agent; and a coatinglayer of a thermoplastic resin covering the core material.

In the thermoplastic resin-coated ammonium polyphosphate of the presentinvention, the foregoing thermoplastic resin is desirably a memberselected from the group consisting of homopolymers of a monomerrepresented by the following general formula 1 which has, in themolecule, 2 to 5 double bonds capable of undergoing polymerization;copolymers of at least two of these monomers represented by the generalformula 1; copolymers of at least one monomer represented by thefollowing general formula 1 with at least one monomer represented by thefollowing general formula 2; or a mixture of these resins:

(in the formula 1, R₁, R₂ and R₃ may be the same or different from oneanother and each represents a member selected from the group consistingof a hydrogen atom, halogen atoms, cyano groups, cyanoalkyl groupshaving 1 to 8 carbon atoms, carboxyl groups, alkyl groups having 1 to 10carbon atoms, alkyl ether groups having 2 to 15 carbon atoms, aminoalkylgroups having 1 to 10 carbon atoms, alkenyl groups having 2 to 12 carbonatoms, alkynyl groups having 2 to 12 carbon atoms, alkyl ester groupshaving 2 to 18 carbon atoms and alkoxy groups having 1 to 14 carbonatoms, with a proviso that if one of the groups R₁, R₂ and R₃ is acarboxyl group or an alkyl ester group having 2 to 18 carbon atoms, theother groups represent groups different from the former and R₄represents a group represented by the following general formula 3 or 4);

(in the formula 2, R₈, R₉, R₁₀ and R₁₁ are the same or different fromeach other and each represents a member selected from the groupconsisting of a hydrogen atom, halogen atoms, cyano groups, cyanoalkylgroups having 1 to 8 carbon atoms, carboxyl groups, alkyl groups having1 to 10 carbon atoms, alkyl ether groups having 2 to 15 carbon atoms,aminoalkyl groups having 1 to 10 carbon atoms, aromatic groups having 6to 32 carbon atoms and alkyl ester groups having 2 to 18 carbon atoms,provided that if one of the groups R₈, R₉, R₁₀ and R₁₁ is a carboxylgroup or an alkyl ester group having 2 to 18 carbon atoms, the othergroups represent groups different from the former);

(in the formula 3, R₁ and R₂ are the same as those defined above inconnection with the general formula 1, respectively and R₅ is a grouprepresented by the following general formula 5, 6, 7 or 8);

(in the formula 4, R₁, R₂ and R₃ are the same as those defined above inconnection with the gneral formula 1, respectively);

(in the formula 5, R₆ and R₇ are the same or different from one anotherand each represents a member selected from the group consisting of ahydrogen atom, halogen atoms, cyano groups, cyanoalkyl groups having 1to 8 carbon atoms, aminoalkyl groups having 1 to 10 carbon atoms,aromatic groups having 6 to 32 carbon atoms and those represented by theforegoing general formula 3 or 4 and p is a numeral ranging from 1 to12);

(in the formula 6, R₆ and R₇ and p are the same as those defined abovein connection with the formula 5, respectively);

—Ar—  7

(in the formula 7, Ar represents an aromatic group having 6 to 32 carbonatoms);

(in the formula 8, R₄ is the same as that defined above in connectionwith the general formula 3).

In the thermoplastic resin-coated ammonium polyphosphate according tothe present invention, the foregoing thermoplastic resin is desirablyused in an amount ranging from 1 to 40 parts by weight per 100 parts byweight of the core material.

In addition, if the thermoplastic resin is a homopolymer of a monomerrepresented by the foregoing general formula 1; a copolymer of thesemonomers; or a copolymer of a monomer represented by the general formula1 with a monomer represented by the general formula 2, the monomer ofFormula 1 is desirably a conjugated diene or non-conjugated dienemonomer having two polymerizable double bonds.

As the core materials suitably used in the present invention, there maybe listed, for instance, ammonium polyphosphate coated with orencapsulated in a thermosetting resin. Examples of such thermosettingresins are melamine resins, modified melamine resins, guanamine resins,epoxy resins, phenolic resins, urethane resins, urea resins and siliconeresins, which may be used alone or in any combination of at least two ofthem.

In addition to the foregoing, examples of core materials usable in thepresent invention further include ammonium polyphosphate coated ormodified with a melamine monomer; and surface-treated ammoniumpolyphosphate comprising ammonium polyphosphate and a surface-treatingagent adhered to, adsorbed or absorbed on or added (adduct) to thesurface of the ammonium polyphosphate. Examples of the surface-treatingagents of this type include saturated or unsaturated fatty acids having6 to 25 carbon atoms, metal salts of saturated or unsaturated fattyacids having 6 to 25 carbon atoms, silane coupling agents, titanatecoupling agents, aluminate coupling agents, anionic surfactants,cationic surfactants, nonionic surfactants, amphoteric surfactants,fluorine atom-containing surfactants and mixture thereof, which may beused alone or in any combination of at least two of them.

In the thermoplastic resin-coated ammonium polyphosphate of the presentinvention, the ammonium polyphosphate desirably comprises phosphorusatoms in an amount ranging from 20 to 31% by weight.

In addition, the thermoplastic resin-coated ammonium polyphosphate ofthe present invention is desirably in the form of fine particles havingan average particle size ranging from 0.1 to 50 μm and preferably 5 to30 μm.

The process for producing the foregoing thermoplastic resin-coatedammonium polyphosphate according to the present invention ischaracterized in that a monomer represented by the foregoing Formula 1and a monomer represented by the foregoing Formula 2 as an optionalcomponent are polymerized on the surface of a core material whichcomprises ammonium polyphosphate and, for instance, a thermosettingresin, a melamine monomer or a surface-treating agent, in the presenceof a catalyst and in the presence or absence of a reaction solvent.

In the process of the present invention, the temperature of thepolymerization reaction of the foregoing monomers desirably ranges from20 to 150° C.

More specifically, in the process for producing the thermoplasticresin-coated ammonium polyphosphate according to the present invention,the polymerization reaction is desirably carried out by introducing acore material and, per 100 parts by weight of the core material, 0.1 to40 parts by weight of a monomer of the general formula 1, 0.1 to 39.9parts by weight of an optional monomer of the general formula 2, 0.1 to10 parts by weight of a catalyst and a reaction solvent in a reactor,and then reacting these ingredients at a temperature ranging from 20 to150° C. for 0.5 to 50 hours.

The flame retardant according to the present invention is characterizedin that it comprises the thermoplastic resin-coated ammoniumpolyphosphate as set forth in claim 1 as an effective component.

BEST MODE FOR CARRYING OUT THE INVENTION

The thermoplastic resin-coated ammonium polyphosphate according to thepresent invention comprises a core material which comprises ammoniumpolyphosphate, and a thermosetting resin, a melamine monomer or asurface-treating agent; and a coating layer of a thermoplastic resin.

In the core material used in the present invention, the component otherthan ammonium polyphosphate (hereinafter sometimes referred to as“secondary component”) serves to control the water-solubility ofammonium polyphosphate and/or to improve the adhesion of thepolyphosphate to the coating layer of the thermoplastic resin.Therefore, it is sufficient that the secondary component is present atleast on the surface of the core material. In other words, the secondarycomponent is present on both the surface and interior of thepolyphosphate or only on the surface of the polyphosphate.

In such a core material, the secondary component and ammoniumpolyphosphate may be present as a reaction product of these twocomponents or a mixture thereof; a coated material obtained by coatingthe latter with the former or a material obtained by encapsulating thelatter with the former; or a material obtained by adhering the former tothe latter, or by adsorbing or absorbing the former on the latter; or inthe form of an adduct thereof. In such a core material, ammoniumpolyphosphate can be made water-insoluble, hardly soluble in water,hydrophobic or water repellent, depending on the properties and the formof existence of the secondary component.

Examples of such core materials include mixed ammonium polyphosphate inwhich ammonium polyphosphate and a melamine monomer, a triazinederivative such as melamine phosphate are uniformly admixed together;coated ammonium polyphosphate in which ammonium polyphosphate is coatedwith or encapsulated in a triazine derivative; adsorbed ammoniumpolyphosphate which carries a triazine derivative adsorbed or absorbedon the surface thereof; hardly water-soluble ammonium polyphosphatewhich is a partial reaction product obtained by partially reacting theammonium polyphosphate with a triazine derivative on the surface of theformer; water-insoluble ammonium polyphosphate in which thepolyphosphate is coated with or encapsulated in a thermosetting resin;and hydrophobic or water-repellent ammonium polyphosphate in which asurface-treating agent, a surfactant or a coupling agent is adsorbed orabsorbed on the surface of the polyphosphate.

It is desirable that such a secondary component be in general used in anamount ranging from 2 to 40% by weight, preferably 3 to 20% by weightand more preferably 5 to 15% by weight on the basis of the total amountof the core material.

In this respect, ammonium polyphosphate as a principal component of thecore material desirably contains phosphorus atoms in a content rangingfrom 20 to 31% by weight, preferably 25 to 30% by weight and morepreferably 27 to 29% by weight (the phosphorus atom content of pureammonium polyphosphate is about 32% by weight).

Examples of the thermosetting resins used for the preparation of theforegoing coated ammonium polyphosphate include melamine resins,modified melamine resins, guanamine resins, epoxy resins, phenolicresins, urethane resins, urea resins and silicone resins, which may beused alone or in combination.

Such coated ammonium polyphosphate may be prepared by a wet curingmethod wherein un-treated ammonium polyphosphate and an epoxy resin,urethane resin, phenolic resin, alkyd resin, urea resin, melamine resin,silicone resin or a mixture of at least two of them in the uncured stateare introduced into a reactor and then cured with heating in water, anorganic solvent or a mixed solvent thereof.

In addition to the foregoing method, the coated ammonium polyphosphatemay likewise be prepared by any known method such as an in-situpolymerization method which comprises the steps of supplying, to areactor, ammonium polyphosphate and a polymerizable monomer aspolymerization components as well as a polymerization catalyst and thenencapsulating ammonium polyphosphate with the polymer of the monomercomponent while establishing such polymerization conditions that athermosetting resin is formed on the particle surface of thepolyphosphate to thus uniformly cover the particles; an interfacialpolymerization method which comprises the steps of separately dissolvingtwo kinds of reactive components in respective two kinds of solventswhich are not miscible with one another and bringing the resulting twosolutions into contact with one another to thus form film-likethermosetting resin at the interface formed between these two liquidphases; a coacervation method which makes use of such a phenomenon(liquid-liquid phase separation) that in a resin/goodsolvent/non-solvent system, a phase rich in the thermosetting resin isseparated from the solvent system; a spray-drying method which comprisesthe steps of spraying a stock solution of a thermosetting resin on fineparticles of ammonium polyphosphate to thus encapsulate thepolyphosphate particles with the thermosetting resin, bringing theencapsulated particles into contact with hot air to thus cure the resinand to simultaneously dry the particles through evaporation of thevolatile components; and a hybridization method which comprises thesteps of applying a mechanical and/or thermal energy mainly comprisingan impact force onto raw resin particles and then fixing the particlesto the surface of ammonium polyphosphate particles or encapsulating thepolyphosphate particles within the resin particles.

In this regard, the surface-treating agent is suitably a compound whichcan not only impart hydrophobicity and water-repellency to ammoniumpolyphosphate particles, but also introduce functional groups into thesurface of the ammonium polyphosphate particles to thus make strongerthe interaction between the coating film and ammonium polyphosphate asthe principal component of the core material and to impart high adhesionthereto in the subsequent process for thermoplastic resin-coating.

Examples of such surface-treating agents include higher fatty acids,coupling agents and surfactants.

More specifically, examples of higher fatty acids are lauric acid,myristic acid, palmitic acid, stearic acid, oleic acid and behenic acid.

Examples of preferred coupling agents are those listed below:

Silane coupling agents represented by the general formula: X_(q)SiY_(4-q) (wherein q is a numeral ranging from 1 to 2; X may be the sameor different when a plurality of Xs are present and each represents ahydrolyzable group such as CH₃O—, C₂H₅O—, CH₃OCH₂CH₂O— or Cl—; and Y maybe the same or different when a plurality of Ys are present and eachrepresents an alkyl group having 1 to 20, preferably 1 to 12 carbonatoms, a vinyl group, an aminoalkyl group having 3 to 6 carbon atoms, aglycidoxy alkyl group having 5 to 9 carbon atoms, a methacryloxy alkylgroup having 5 to 10 carbon atoms, a vinylbenzyl group-conatining group,a chloroalkyl group having 2 to 6 carbon atoms or an epoxy cyclohexylethyl group);

Four- to six-coordinated titanate type coupling agents such as isopropyltriisostearoyl titanate, isopropyl tris(dioctylpyrophosphate) titanate,isopropyl tri(N-aminoethylaminoethyl) titanate, tetraoctylbis(di-tridecylphosphite) titanate,tetra(2,2-diallyloxymethyl-1-butyl)-bis(di-tridecyl) phosphite titanate,bis(dioctylpyrophosphate) oxyacetate titanate, bis(dioctylpyrophosphate)ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tridodecyl benzenesulfonyl titanate,isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctylphosphate)titanate, isopropyl tricumylphenyl titanate and tetraisopropylbis(dioctylphosphite) titanate;

Aluminate type coupling agents such as acetoalkoxy aluminumdiisopropylate, alkoxy aluminum diisopropylate and alkoxy aluminumacetylacetonate;

Zircoaluminate type coupling agents such as alkoxy zircoaluminumdiisopropylate and alkoxy zircoaluminum acetylacetonate; and

Phosphate type coupling agents.

In addition, surfactants may be any conventionally known ones including,for instance, anionic surfactants, cationic surfactants, nonionicsurfactants, amphoteric surfactants and fluorine atom-containingsurfactants.

Examples of anionic surfactants include saturated fatty acid saltshaving 10 to 32 and preferably 12 to 22 carbon atoms, for instance,higher carboxylic acid salts such as lauric acid salts, myristic acidsalts, palmitic acid salts, stearic acid salts and oleic acid salts;condensates of higher fatty acids with amino acids such asN-acyl-N-methylglycine, N-acyl-N-methyl- β-alanine and N-acyl-glutamicacid, and salts thereof; alkyl ether carboxylic acid salts; acylatedpeptides; alkylbenzenesulfonic acid salts; alkylnaphthalenesulfonates;naphthalenesulfonatesformaldehyde polycondensates;dialkylsulfosuccinates; alkylsulfoacetates; α-olefin sulfonates;N-acylmethyl taurine; Turkey red oil; higher alcohol sulfates; secondaryhigher alcohol sulfates; alkyl ether sulfates; secondary higher alcoholethoxysulfates; polyoxyethylene alkylphenyl ether sulfates;monoglysulfate; sulfates of fatty acid alkylolamides; alkyl etherphosphoric acid monoester salts; alkyl ether phosphoric acid diestersalts; alkyl ether phosphoric acid triesters; alkyl phosphoric acidmonoester salts; alkyl phosphoric acid diester salts; and alkylphosphoric acid triesters.

Examples of cationic surfactants are higher aliphatic amine salts suchas those obtained by neutralizing primary, secondary and tertiary higheralkylamines having 12 to 54 carbon atoms with inorganic acids such ashydrochloric acid and sulfuric acid or organic acids such as aceticacid, lactic acid and citric acid; aliphatic quaternary ammonium saltshaving 12 to 40 carbon atoms; benzalkonium salts; benzethonium chloride;alkyl pyridinium salts; and imidazolinium salts and examples ofamphoteric surfactants include alkyl dimethyl betaines; aminocarboxylicacid salts; imidazolinium betaine; and lecithin.

In addition, examples of nonionic surfactans are polyoxyethylene alkylethers prepared by addition-polymerization of aliphatic primary alcoholseach having 12 to 22 carbon atoms and ethylene oxide; polyoxyethylenesecondary alcohol ethers; polyoxyethylene alkylphenyl ethers;polyoxyethylene sterolethers; polyoxyethylene lanolin derivatives;polyethylene alkyl phenol ether formaldehyde condensates;polyoxyethylene polyoxypropylene block copolymers; polyoxyethylenepolyoxypropylene alkyl ether; polyoxyethylene glycerin fatty acidesters; polyoxyethylene castor oil and hydrogenerated castor oil;polyoxyethylene sorbitan fatty acid esters; polyoxyethylene sorbitolfatty acid esters; polyethylene glycol fatty acid esters; fatty acidmonoglycerides; polyglycerin fatty acid esters; sorbitan fatty acidesters; propylene glycol fatty acid esters; sucrose fatty acid esters;fatty acid alkanolamides; polyoxyethylene fatty acid amides;polyoxyethylene alkylamines; and alkylamine oxides.

Moreover, fluorine atom-containing surfactants herein used are thosehaving, as hydrophobic groups, fluorocarbon or perfluorocarbon groups.Examples of such fluorine atom-containing surfactants includefluoroalkyl carboxylic acids whose alkyl group has 2 to 10 carbon atoms,disodium N-perfluorooctanesulfonyl glutamic acid, sodium3-(fluoroalkyl(C₆ to C₁₁)oxy)-1-alkyl(C₃ to C₅)-sulfonate, sodium3-(ω-fluoroalkanoyl(C₆ to C₈)-N-ethylamino)-1-propanesulfonate,N-[3-(perfluorooctanesulfonamido)propyl]N,N-dimethyl-N carboxymethyleneammonium betaine, fluoroalkyl(C₁₁ to C₂₀)carboxylic acids,perfluoroalkyl(C₇ to C₁₃)carboxylic acids, perfluorooctanesulfonicdiethanolamide, perfluoroalkyl(C₄ to C₁₂)sulfonic acid salts,N-propyl-N-(2-hydroxyethyl)perfluorooctanesulfonamides,perfluoroalkyl(C₆ to C₁₀)sulfonamidopropyl trimethyl ammonium salts,perfluoroalkyl(C₆ to C₁₀)-N-ethylsulfonyl glycine salts, phosphoric acidbis(Nperfluorooctylsulfonyl-N-ethylaminoethyl) and monoperfluoroalkyl(C6to C₁₆)ethyl phosphoric acid esters.

In the present invention, the foregoing surface-treating agents may beused in combination in any amount. In this regard, the surface-treatingmethods usable herein, which make use of these surface-treating agents,may be known ones such as a wet method which comprises the steps ofpreparing a solution of a surface-treating agent by diluting it with,for instance, water, an aqueous acetic acid solution or water-alcoholmixed solvent and then immersing a subject to be treated in theresulting solution; and a dry method which comprises the step of addingthe surface-treating agent or a solution thereof to a subject withstirring by, for instance, spraying. In addition, if a coupling agent isused as the surface-treating agent, it is possible to use a primermethod which makes use of a primer prepared by homo-polymerizing thecoupling agent or reacting it with another prepolymer.

As the core material used in the present invention may be those preparedby the method described above and those commercially available andexamples of such commercially available core materials are HostaflamAP-462 (trade name of a product manufactured by Hoechst Company),Sumisafe-PM (trade name of a product manufactured by Sumitomo ChemicalCo., Ltd.), TERRAJU-M30 (trade name of a product manufactured by ChissoCorporation), TERRAJU-M40 (trade name of a product manufactured byChisso Corporation), TERRAJU-C30 (trade name of a product manufacturedby Chisso Corporation), TERRAJU-C40 (trade name of a productmanufactured by Chisso Corporation), TERRAJU-C60 (trade name of aproduct manufactured by Chisso Corporation), TERRAJU-C70 (trade name ofa product manufactured by Chisso Corporation) and TERRAJU-C80 (tradename of a product manufactured by Chisso Corporation).

In the present invention, the thermoplastic resin for covering such acore material is desirably those having good adhesion to the surface ofthe core material and capable of forming a uniform coating film thereon.

Moreover, the method for applying the coating film comprising thesethermoplastic resin to the surface of the core material may likewiseappropriately be selected depending on the factors such as the kinds ofmonomers for the production of the resins and the kinds of resinsprepared and, for instance, it is possible to properly employ theencapsulation technique which is used for the preparation of corematerials provided thereon with a coated film of a thermosetting resin.

The thermoplastic resins used for covering the core material in thepresent invention particularly preferably include, for instance,homopolymers of specific monomers (hereinafter also referred to as“first monomer”) having 2 to 5 double bonds capable of undergoingpolymerization, in each molecule; copolymers of at least two of thefirst monomers; and copolymers of at least one of the first monomer withat least one monomer (hereinafter also referred to as “second monomer”)having one double bond capable of undergoing polymerization, in themolecule. These polymers and copolymers may be used alone or in anycombination of at least two of them, as the thermoplastic resin.

The first monomer having 2 to 5 double bonds capable of undergoingpolymerization in the molecule may be represented by the followinggeneral formula 1:

In the formula 1, R₁, R₂ and R₃ may be the same or different from oneanother and each represents a member selected from the group consistingof a hydrogen atom, halogen atoms, cyano groups, cyanoalkyl groupshaving 1 to 8, preferably 1 to 6 carbon atoms, carboxyl groups, alkylgroups having 1 to 10, preferably 1 to 6 carbon atoms, alkyl ethergroups having 2 to 15, preferably 2 to 10 carbon atoms, aminoalkylgroups having 1 to 10, preferably 2 to 6 carbon atoms, alkenyl groupshaving 2 to 12, preferably 2 to 8 carbon atoms, alkynyl groups having 2to 12, preferably 2 to 8 carbon atoms, alkyl ester groups having 2 to18, preferably 2 to 10 carbon atoms and alkoxy groups having 1 to 14,preferably 1 to 8 carbon atoms, with the proviso that if one of thegroups R₁, R₂ and R₃ is a carboxyl group or an alkyl ester group, theother groups represent groups different from the former.

Examples of the foregoing halogen atoms are fluorine, chlorine, bromineand iodine atoms; and

Examples of the cyanoalkyl groups include those represented by thegeneral formula:

—C_(n)H_(2n).CN

(wherein n is an integer ranging from 1 to 8) and specific examplesthereof include linear cyanoalkyl groups such as cyanomethyl group,cyanoethyl group, cyanopropyl group, cyanobutyl group, cyanopentyl groupand cyanohexyl group; and alkyl-substituted groups of these linearcyanoalkyl groups such as 1-methylcyanoethyl group, 2-methylcyanoethylgroup, 1,1-dimethylcyanoethyl group, 1,2-dimethylcyanoethyl group,2,2-dimethylcyanoethyl group, 1,2-dimethylcyanopropyl group,1,3-dimethylcyanopropyl group, 1-ethylcyanoethyl group,2-ethylcyanoethyl group, 1,1-diethylcyanoethyl group,1,2-diethylcyanoethyl group, 2,2diethylcyanoethyl group,1,2-diethylcyanopropyl group and 1,3-diethylcyanopropyl group;

Examples of the alkyl groups are those represented by the generalformula:

—C_(n)H_(2n+1)

(wherein n is an integer ranging from 1 to 10) such as methyl group,ethyl group, propyl group, isopropyl group, 2-methylethyl group, butylgroup, isobutyl group, 3-methylpropyl group, 3-ethylpropyl group,2-methylbutyl group, 3-methylbutyl group, 2-methylpentyl group,3-methylhexyl group, 4-methylhexyl group, pentyl group and hexyl group;

Examples of the alkyl ether groups are those represented by the generalformula:

—C_(n)H_(2n).O.C_(m)H_(2m+1)

(wherein n and m each is an integer ranging from 1 to 14, provided thatthe sum of n and m falls within the range of from 2 to 15) such asmethoxymethyl group, methoxyethyl group, methoxypropyl group,methoxypentyl group, methoxyhexyl group, ethoxymethyl group, ethoxyethylgroup, ethoxypropyl group, ethoxypentyl group and ethoxyhexyl group;

Examples of the aminoalkyl groups include those represented by thegeneral formula:

—C_(n)H_(2n).NH₂

(wherein n is an integer ranging from 1 to 10) such as aminomethylgroup, aminoethyl group, aminopropyl group, aminoisopropyl group,aminobutyl group, aminoisobutyl group, aminopentyl group and aminohexylgroup;

Examples of the alkenyl groups are those represented by the generalformula:

—C_(n)H_(2n−1)

(wherein n is an integer ranging from 2 to 8) such as vinyl group, allylgroup, propenyl group, butenyl group, pentenyl group, hexenyl group,heptenyl group, octenyl group and alkyl-substituted derivatives thereof;

Examples of the alkynyl groups are those represented by the generalformula:

—C_(n)H_(2n−2)

(wherein n is an integer ranging from 2 to 12) such as ethynyl group,propynyl group, butynyl group, pentynyl group, hexynyl group, peptynylgroup, octynyl group and alkyl-substituted derivatives thereof; and

Examples of the alkyl ester groups are those represented by the generalformula:

—C(O)OC_(n)H_(2n+1)

(wherein n is an integer ranging from 2 to 10) such as methyl estergroup, ethyl ester group, propyl ester group, butyl ester group, pentylester group, hexyl ester group and alkyl-substituted derivativesthereof.

In addition, the group R₄ represents a group represented by thefollowing general formula 3 or 4:

In the formula 3, R₁ and R₂ are the same as those defined above inconnection with the general formula 1, respectively and in the formula4, R₁, R₂ and R₃ are the same as those defined above in connection withthe gneral formula 1, respectively.

Moreover, the group R₅ appearing in Formula 3 is a group represented bythe following general formula 5, 6, 7 or 8:

(in the formula 5, R₆ and R₇ are the same or different from one anotherand each represents a member selected from the group consisting of ahydrogen atom, halogen atoms, cyano groups, cyanoalkyl groups having 1to 8, preferably 1 to 6 carbon atoms, aminoalkyl groups having 1 to 10,preferably 2 to 6 carbon atoms, aromatic (aryl) groups having 6 to 32,preferably 6 to 12 carbon atoms and those represented by the foregoinggeneral formula 3 or 4 and p is a numeral ranging from 1 to 12 andpreferably 1 to 6);

(in the formula 6, R₆ and R₇ and p are the same as those defined abovein connection with the formula 5, respectively);

—Ar—  7

(in the formula 7, Ar represents an aromatic group having 6 to 32,preferably 6 to 12 carbon atoms); and

(in the formula 8, R₄ is the same as that defined above in connectionwith the general formula 3).

In the foregoing Formula 5, specific examples of the halogen atom,cyanolkyl group, alkyl group, alkyl ether group, aminoalkyl group,alkenyl group, alkynyl group and alkyl ester group may be the same asthose listed above in connection with the general formula 1. Moreover,in the foregoing Formulas 1 and 3 to 8, the groups represented by R₁ toR₈ are selected in such a manner that the total number of double bondscapable of undergoing polymerization present in each monomer molecule isequal to 2 to 5 and preferably 2 to 3.

In the present invention, such a first monomer is particularlypreferably a conjugated diene monomer or a non-conjugated diene monomerhaving two polymerizable double bonds in the molecule.

Specific examples of the first monomers thus detailed above are thoselisted below:

1,2-divinyl benzene, 1,3-divinyl benzene, 1,4-divinyl benzene,1,2-diallyl phthalate, 1,2-diallyl phthalate, 1,4-diallyl phthalate,divinyl ether, allyl vinyl ether, propenyl vinyl ether, allyl-α-methylvinyl ether, butadiene, chloroprene, fluoroprene, cyanoprene,bromoprene, 1,4-pentadiene, 1,5-hexadiene, 1,6-heptadiene,1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,10-undecadiene,1,11-dodecadiene, 1,12-tridecadiene, 1,13-tetradecadiene,1,17-octadecadiene, 1,21-docosadiene, allene, allene derivatives,2,5-dimethyl-1,5-hexadiene, cis-1,5,9-decatriene,trans-1,3,7-octatriene, 1-vinyl-3-methylene cyclopentane,2,5-diphenyl-1,5-hexadiene, 2-phenyl-1,5-hexadiene,3-methyl-1,5-hexadiene, 3-phenyl-1,5-hexadiene,3-methyl-4-phenyl-1,5-hexadiene and 3-vinyl-1,5-hexadiene;

2,6-diphenyl-1,6-heptadiene, 2,7-diphenyl-1,7-octadiene,3-phenyl-1,5-heptadiene, 2,6-dicarbethoxy-1,6-heptadiene,2,6-dicarboxy-1,6-heptadiene, 2,6-dicyano-1,6-heptadiene,4,4-dicarbethoxy-1,6-heptadiene, 4-acetyl-4-carbethoxy-1,6-heptadiene,4-carboxy-1,6-heptadiene, 4-acetyl-1,6-heptadiene,4,4-diacetyl-1,6-heptadiene, 4-cyano-4-carbethoxy-1,6-heptadiene,4-cyano-4-carboxy-1,6-heptadiene, 4-cyano-1,6-heptadiene,2,6-dichloro-4,4-dicarbethoxy-1,6-heptadiene,2,6-dichloro-3-carbethoxy-1,6-heptadiene,4-allyl-4-hydroxy-1,6-heptadiene, 4-allyl-4-acetoxy-1,6-heptadiene,trans-1,2-divinyl cyclobutane, cis-1,2-divinyl cyclobutane,trans-1,2-dimethyl-1,2-divinyl cyclobutane, trans-1-isopropenyl-2-vinylcyclobutane and trans-1,2-diisopropenyl cyclobutane;

cis-1,2-divinyl cyclopentane, cis-1,3-divinyl cyclopentane,trans-1,3-divinyl cyclopentane, cis-1,2-divinyl cyclohexane,trans-1,2-divinyl cyclohexane, cis-1,3-divinyl cyclohexane,trans-1,3-divinyl cyclohexane, trivinyl cyclohexane, 1,2,4-trimethylenecyclohexane, 1,3,5-trimethylene cyclohexane, 1,3,5,7-tetramethylenecyclooctane, 1,4-dimethylene cyclohexane, 1-methylene-4-vinylcyclohexane, divinyl ketone, divinyl acetylene, triallyl isocyanurate,triallyl cyanurate, triacryl formal, trimethallyl isocyanurate,diglycidyl bisphenol A diacrylate, dipentaerythritolmonohydroxyacrylate, trimethylolpropane triacrylate, neopentyl glycolhydroxypivalic acid ester diacrylate, 1,4-butanediol diacrylate,2-propenoic acid[2-[1,1-dimethyl-2-[(1-oxo-2-propenyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methylester, pentaerythritol triacrylate, trimethacrylic acidtrimethylolpropane, dimethacrylic acid ethylene glycol, dimethacrylicacid triethylene glycol, dimethacrylic acid tetraethylene glycol,dimethacrylic acid 1,3-butylene glycol, allyl methacrylate,N,N′-methylenebis(acrylamide), triallyl trimellitate,3,9-divinyl-2,4,8,10-tetraoxaspiro[5,5]undecane. These first monomersmay be used alone or in any combination.

The secondary monomer optionally used in combination with the firstmonomer in the preparation of the thermoplastic resin suitably used as acoating material for the core material in the present invention is onecarrying one polymerizable double bond in the molecule and may berepresented by the following general formula 2:

In the formula 2, R₈, R₉, R₁₀ and R₁₁ are the same or different fromeach other and each represents a member selected from the groupconsisting of a hydrogen atom, halogen atoms, cyano groups, cyanoalkylgroups having 1 to 8, preferably 1 to 6 carbon atoms, carboxyl groups,alkyl groups having 1 to 10, preferably 1 to 6 carbon atoms, alkyl ethergroups having 2 to 15, preferably 2 to 10 carbon atoms, aminoalkylgroups having 1 to 10, preferably 2 to 6 carbon atoms, aromatic (aryl)groups having 6 to 32, preferably 6 to 12 carbon atoms and alkyl estergroups having 2 to 18, preferably 2 to 10 carbon atoms, provided that ifone of the groups R₈, R₉, R₁₀ and R₁₁ is a carboxyl group or an alkylester group, the other groups represent groups different from theformer).

In the foregoing Formula 5, specific examples of the halogen atom,cyanoalkyl group, alkyl group, alkyl ether group, aminoalkyl group andalkyl ester group may be the same as those listed above in connectionwith the general formula 1 and examples of aromatic groups are phenylgroup, phenyl groups substituted with 1 to 5 alkyl groups, biphenylgroup and naphthyl group.

In addition, specific examples of such monomers each having onepolymerizable double bond in the molecule include those listed below:

Ethylene, propylene, 1-butene, isobutylene, 3-methyl-1-butene,4-methyl-1-pentene, 1-hexene, 1-octene and 1-decene;

Styrene, α-methylstyrene, vinyltoluene, chlorostyrene, cyanostyrene,aminostyrene, hydroxystyrene, vinylnaphthalene, vinylanthracene,2-vinylphenanthrene and 3-vinylphenanthrene;

Acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid,acrylic acid esters, methacrylic acid esters, cyclohexyl methacrylate,benzyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropylmethacrylate, methylaminoethyl methacrylate, diethylaminoethylmethacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate,α-cyanoacrylic acid ester, α-halogenoacrylic acid ester, acrylamide,methacrylamide and diacetone acrylamide;

Allyl chloride, allyl alcohol, allyl amine, allyl acetone, allylaldehyde, allyl ester, allyl methyl ether, allyl ethyl ether, allylcarbamide, allyl glycerin, allyl acetic acid, allyl thioalcohol, allylthiocarbamide, allyl thiocarboimide, allyl thiourea and allyl urea;

Vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride,vinylidene fluoride, fluorostyrene, vinyl acetate, vinyl laurate andvinyl salicylate;

Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropylvinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, n-hexyl vinylether, n-octyl vinyl ether, phenyl vinyl ether, o-cresyl vinyl ether,p-cresyl vinyl ether, p-chlorophenyl vinyl ether, α-naphthyl vinyl etherand β-naphthyl vinyl ether; and

1-Buten-3-on, acrylophenone, 2-vinylpyridine, 4-vinylpyridine and2-methyl-5-vinylpyridine. These secondary monomers may be used alone orin any combination of at least two of them.

The polymerization or copolymerization reaction of the first monomer andthe optional secondary monomer can be carried out using a polymerizationinitiator used in the usual radical polymerization reaction. The polymeror copolymer prepared from the monomer including the first monomer is atwo- or three-dimensionally cross-linked thermoplastic resin and it ishardly soluble or almost insoluble in the usual organic solvents due tothe cross-linked structure. For this reason, the ammonium polyphosphateparticles coated with this thermoplastic resin is excellent inresistance to organic solvents.

The ammonioum polyphosphate obtained by coating the core materialdescribed above with a thermoplastic resin having such a structure canconveniently be prepared by the following process according to thepresent invention.

In other words, according to the process of the present invention, thethermoplastic resin-coated ammonium polyphosphate is produced bysubjecting a monomer represented by the foregoing general formula 1 anda secondary monomer represented by the general formula 2 as an optionalcomponent to a polymerization reaction, on the surface of the corematerial defined above, in the presence of polymerization catalyst, withor without using a reaction solvent.

More specifically, there are first added, to a reactor, preferably areactor provided with heating and stirring means or heating and kneadingmeans, the core material, 0.1 to 40 parts by weight, preferably 2 to 20parts by weight of the first monomer, 0.1 to 39.9 parts by weight,preferably 2 to 10 parts by weight of the optional secondary monomer and0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight of apolymerization initiator, per 100 parts by weight of the core material,followed by admixing these ingredients.

At this stage, a reaction solvent may be used in an amount ranging from10 to 500 parts by weight and examples of such reaction solvents arewater or organic solvents inert to each monomer, which may be used aloneor in combination.

Examples of the polymerization initiators usable in the polymerizationreaction include organic peroxides such as benzoyl peroxide, acetylperoxide, t-butylhydroxy peroxide, cumene hydroperoxide, di-t-butylperoxide, lauroyl peroxide, dimethyl α, α′-azodiisobutyrate, succinicacid peroxide, dicumene peroxide and dichlorobenzoyl peroxide; inorganicperoxides such as potassium persulfate, ammonium persulfate, hydrogenperoxide and sodium perborate; azo compounds such as α,α′-azodiisobutyronitrile, azodicyclohexylcarbonitrile,phenylazotriphenyl methane. All of these peroxides may be commerciallyavailable ones.

Then the mixture in the reactor is heated to a temperature ranging from20 to 150° C., preferably 50 to 100° C. with stirring and the reactionis continued over a time sufficient for the completion of thepolymerization reaction, for instance, 0.5 to 50 hours to thus form acoating layer of a cross-linked polymer on the surface of the corematerial and to thus give the thermoplastic resin-coated ammoniumpolyphosphate according to the present invention.

In the thermoplastic resin-coated ammonium polyphosphate of the presentinvention as has been described above, the amount of the thermoplasticresin coating layer ranges from 1 to 40 parts by weight and preferably 5to 20 parts by weight per 100 parts by weight of the core material.

In addition, the thermoplastic resin-coated ammonium polyphosphate ofthe present invention desirably has an average particle size rangingfrom 0.1 to 50 μm and preferably 5 to 30 μm from the viewpoint of, forinstance, the dispersibility in a resin composition used as a flameretadant.

A flame retardant containing, as an effective component, thethermoplastic resin-coated ammonium polyphosphate of the presentinvention, i.e., the flame retardant according to the present inventionmay comprise only the thermoplastic resin-coated ammonium polyphosphate;or a combination thereof with other known flame retardants, forinstance, inorganic flame retardants such as phosphoric acid esters,condensed phosphoric acid esters, amorphous phosphorus, coated amorphousphosphorus, magnesium hydroxide, aluminum hydroxide, phosphoric acidsalts and boric acid salts; and other components capable of improvingthe flame retardancy of the flame retardant of the invention if theformer is used in combination with the latter, for instance, polyhydricalcohols such as pentaerythritol and tris(2-hydroxyethyl)isocyanurate,and/or nitrogen atom-containing compounds such as melamine, melaminecyanurate, melamine resins, polyamides and polyimides.

In the flame retardant according to the present invention, thethermoplastic resin-coated ammonium polyphosphate included therein as aneffective component is excellent in the water resistance, resistance toorganic solvents and chemical resistance (resistance to acids andrsistance to alkalis) and also has a high affinity for thermoplasticresins. Therefore, the flame retardant is quite suitable for theincorporation, in particular, into compositions for obtaining resinmolded articles.

EFFECTS OF THE INVENTION

The thermoplastic resin-coated ammonium polyphosphate according to thepresent invention is excellent in water resistance and resistance toorganic solvents or chemical resistance such as resistance to acids andresistance to alkalis and if it is incorporated into a thermosettingresin or thermoplastic resin-based molding material as a component forthe flame retardant added thereto, it can provide a molded article whichdoes not show any substantial reduction in the mechanical strength andhas a high effect of controlling, for instance, hygroscopicity.Therefore, the thermoplastic resin-coated ammonium polyphosphateaccording to the present invention can be suitably used as a flameretardant component for, for instance, electric and eletronic parts,materials for motorcars and construction materials.

EXAMPLES

The present invention will hereinafter be described in more detail withreference to the following Examples and Comparative Examples, but thepresent invention is not restricted to these specific Examples at all.Moreover, in these Examples and Comparative Examples, the qualityevaluation was carried out according to the methods described below.

(1) Method for Evaluation of Water-Solubility

The amount of the water-soluble components present in the product wasdetermined as follows. Each of the products (10 g) prepared in Examplesand Comparative Examples was suspended in 90 g of pure water to give asuspension. After shaking the suspension at a temperature of 25° C. for24 hours, it was centrifuged and then the resulting supernatant wasfiltered through filter paper of 0.45 μm. A predetermined amount of theresulting filtrate was taken in a weighing bottle, followed byevaporation to dryness thereof in a dryer and determination of thewater-solubility of the sample according to the following formula 1. Inthis respect, the lower the numerical value obtained, the higher thewater-resistance of the sample.$\text{Water-Solubility~~(\%)} = \frac{{W(R)} \times {W({PW})} \times 100}{{W(S)} \times \left( {{W(F)} - {W(R)}} \right)}$

wherein W(R) means the weight of the residue remaining after theevaporation to dryness; W(PW) represents the weight of pure water; W(S)represents the weight of the sample; and W(F) means the weight of thefiltrate.

(2) Method for the Evaluation of Resistance to Acids

Each of the products (10 g) prepared in Examples and ComparativeExamples was suspended in 90 g of a 0.1N hydrochloric acid solution toprepare a 10% by weight suspension. After shaking the suspension at atemperature of 25° C. for one hour, it was centrifuged and then theresulting supernatant was filtered through filter paper of 0.45 μm. Apredetermined amount of the filtrate was dispensed in a weighing bottle,followed by evaporation to dryness thereof in a dryer and determinationof the solubility of each sample in the acid solution according to therelation similar to the foregoing formula 1. In this respect, the lowerthe numerical value obtained, the higher the resistance to acids of thesample.

(3) Method for the Evaluation of Resistance to Alkalis and Ions

After shaking 90 g of a 0.1N sodium hydroxide or sodium chloride aqueoussolution at a temperature of 25° C. for one hour, about 5 g of theaqueous solution was taken in a weighing bottle, followed by evaporationto dryness to thus determine the blank value.

Then each of the products (10 g) prepared in Examples and ComparativeExamples was suspended in 90 g of a 0.1N sodium hydroxide or sodiumchloride aqueous solution to prepare a 10% by weight suspension. Aftershaking the suspension at a temperature of 25° C. for one hour, it wascentrifuged and then the resulting supernatant was filtered throughfilter paper of 0.45 μm. About 5 g of the filtrate was correctlydispensed in a weighing bottle, followed by evaporation to drynessthereof in a dryer to thus determine the solubility of the sample in theaqueous alkali or salt solution according to the following formula 2. Inthis respect, the lower the numerical value obtained, the higher theresistance to alkalis of the sample.$\text{Solubility~~(\%)} = \frac{\left( {{W(R)} - {Vb}} \right) \times {W({HCl})} \times 100}{{W(S)} \times \left\{ {{W(F)} - \left( {{W(R)} - {Vb}} \right)} \right\}}$

wherein W(R), W(S) and W(F) are the same as those defined above inconnection with the foregoing formula 1, Vb represents the blank valueand W(HC1) represents the weight of HCl.

(4) Method for the Evaluation of Resistance to Organic Solvents

Each of the products obtained in Examples and Comparative Examples (10 geach) was suspended in 90 g of toluene to prepare a 10% by weightsuspension. After shaking the suspension at a temperature of 25° C. forone hour, it was centrifuged and then the resulting supernatant wasfiltered through filter paper of 0.45 μm. About 5 g of the filtrate wascorrectly dispensed in a weighing bottle, followed by evaporation todryness thereof in a dryer to thus determine the solubility of thesample in the oganic solvent according to the relation similar to theforegoing formula 1. In this respect, the lower the numerical valueobtained, the higher the resistance to organic solvents of the sample.

(5) Method for Evaluating Water Resistance and Flame Retardancy of FlameRetardant Resin-Molded Article

There were preliminarily admixed sufficiently 100 parts by weight of abisphenol A type epoxy resin Epicote 828 (trade name of a productmanufactured by Yuka Shell Epoxy Co., Ltd.) and Epomate LX-IN (tradename of a product manufactured by Yuka Shell Epoxy Co., Ltd.) as acuring agent. Then each (40 parts by weight) of the products obtained inExamples and Comparative Examples was added to the mixture, followed byadditional mixing. The resulting resin composition was poured into amold having a size of 100 mm long×100 mm wide so that the thickness ofthe composition was equal to about 3 mm, followed by degassing underreduced pressure, then curing the composition by allowing it to stand at50° C. for 24 hours to thus give a flat plate. Specimens for waterresistance test (40 mm long×40 mm wide) and for flame retardancy test(100 mm long×6 mm wide) were cut from the resulting plate using a bandsaw.

The water resistance was determined by allowing each specimen to standat 80° C. for 7 days while immersing it in 200 g of pure water and thendetermination of the electric conductivity (10⁻³Ω⁻¹m⁻¹) of the immersionliquid and calculation of the difference between the measured value andthe blank value, which was used as the indication for the waterresistance. The release of the hydrolyzate originated from ammoniumpolyphosphate causes an increase of the electric conductivity.

The flame retardancy was evaluated according to the method specified inJIS K7201 (Combustion test methods for polymeric materials based on theoxygen index).

(6) Impact Resistance Test

This was evaluated according to the method defined in JIS K7110 (Izodimpact test for rigid plastics). In this respect, the specimen used wasprepared as follows:

To a Henschel (trade name) mixer, there were added 100 parts by weightof a polystyrene resin (Daicel Styrol R63) and 30 parts by weight ofammonium polyphosphate obtained in each of Examples and ComparativeExamples, followed by stirring and mixing for 3 minutes, kneading themixture at a melting and kneading temperature of 210° C. in a twin-screwextruder (PCM-30 manufactured by Ikegai Corporation), extrusion thereofin the form of strands and cutting the strands into pellets. Afterdrying the pellets at 80° C. for 8 hours, the pellets were molded into aspecimen having a size of 127 mm long×12.7 mm wide×3 mm thick at amolding temperature of 210° C. in an injection molding machine (N40B-IImanufactured by The Japan Steel Works, Ltd.). The both ends (32 mm each)were cut off from the molded article and a notch having a depth of 2.54mm and an R (curvature radius) at the tip of 0.25 mm was formed on thecenter of the central part of the article which was used as a testpiece.

The core materials used in Examples and Comparative Examples areexpressed by the following abbreviations:

APP-1: Melamine-coated ammonium polyphosphate prepared in the followingReference Example 1;

APP-2: Formaldehyde-modified melamine-coated ammonium polyphosphateprepared in the following Reference Example 2;

APP-3: Hostaflam AP462 (manufactured by Hoechst Company); ammoniumpolyphosphate covered with melamineformaldehyde polycondensate.

Reference Example 1

To a 5-liter volume kneader pre-heated to a temperature ranging from 270to 300° C., there were added 1900 parts by weight of ammoniumpolyphosphate having the crystalline form II and an average particlesize of about 15 μm and 100 parts by weight of melamine (reagent grade)and the resulting mixture was maintained at a temperature ranging from260 to 300° C. for 6 to 7 hours with stirring. After cooling,melamine-coated ammonium polyphosphate (APP-1) was obtained as a corematerial in an amount of about 2000 parts by weight. The averageparticle size of the melamine-coated ammonium polyphosphate was found tobe about 17 μm. The coated ammonium polyphosphate was observed with anelectron microscope and as a result, it was confirmed that the surfaceof ammonium polyphosphate particles were approximately uniformly coatedwith melamine.

Reference Example 2

To a 5-liter volume reaction vessel equipped with a heater, a stirrerand a refluxing device, there were added 1000 parts by weight of themelamine-coated ammonium polyphosphate prepared in Reference Example 1,116 parts by weight of a formalin solution having a concentration of 37%by weight and 2000 parts by weight of an aqueous methanol solutionhaving a concentration of 12% by weight and these ingredients werereacted at a refluxing temperature for 2 hours. The reaction system wascooled, filtered and then dried to give about 1000 parts by weight of aformaldehyde-modified product (APP-2) as a core material. The averageparticle size of the formaldehyde-modified product was found to be about17 μm.

Example 1

To a 500 ml volume reactor equipped with a stirrer, a thermometer, arefluxing device and an inlet port, there were added 100 parts by weightof APP-1 prepared above, 7 parts by weight of styrene monomer, 3 partsby weight of divinylbenzene, 2 parts by weight of potassium persulfate,200 parts by weight of water and 50 parts by weight of methanol,followed by mixing them at ordinary temperature. Then the reactionsystem was heated to 80° C. and these ingredients were reacted at thattemperature for 6 hours. After cooling the reaction solution, it wasfiltered, washed with water and then dried to give 110 parts by weightof thermoplastic resin-coated ammonium polyphosphate. The product wasobserved with an electron microscope and as a result, it could beconfirmed that the ammonium polyphosphate particles were uniformlycoated with the resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was subjected to the foregoing various kinds of qualityevaluation tests. The results thus observed are summarized in thefollowing Table 1.

Example 2

The same procedures used in Example 1 were repeated except that APP-2prepared above was substituted for APP-1 used in Example 1 to thus give110 parts by weight of thermoplastic resin-coated ammoniumpolyphosphate. The surface of the product was observed with an electronmicroscope and as a result, it could be confirmed that the ammoniumpolyphosphate particles were uniformly coated with the resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was subjected to the foregoing various kinds of qualityevaluation tests. The results thus obtained are summarized in thefollowing Table 1.

Example 3

The same procedures used in Example 1 were repeated except that theamount of the styrene monomer and divinylbenzene were changed to 10.5parts by weight and 4.5 parts by weight, respectively to thus give 115parts by weight of thermoplastic resin-coated ammonium polyphosphate.The surface of the product was observed with an electron microscope andas a result, it could be confirmed that the ammonium polyphosphateparticles were uniformly coated with the resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was examined by the foregoing various kinds of qualityevaluation tests. The results thus obtained are summarized in thefollowing Table 1.

Example 4

To a desk mixer (laboratory mixer), there were added 100 parts by weightof APP-2 prepared above and 2 parts by weight of oleic acid, followed bysufficient mixing and heating in an oven maintained at 50° C. for onehour to thus obtain oleic acid-treated APP-2. Then, to a 500 ml volumereactor equipped with a stirring machine, a thermometer, a refluxingdevice and an inlet port, there were added 100 parts by weight of theoleic acid-treated APP-2, 7 parts by weight of styrene monomer, 3 partsby weight of divinylbenzene, 2 parts by weight of potassium persulfate,200 parts by weight of water and 50 parts by weight of methanol,followed by mixing them at ordinary temperature. Then the reactionsystem was heated to 80° C. and these ingredients were reacted at thattemperature for 6 hours. After cooling the reaction solution, it wasfiltered, washed with water and then dried to give 110 parts by weightof thermoplastic resin-coated ammonium polyphosphate. The particlesurface of the product was observed with an electron microscope and as aresult, it could be confirmed that the ammonium polyphosphate particleswere uniformly coated with the resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was inspected for various properties according to theforegoing various kinds of quality evaluation tests. The results thusobserved are summarized in the following Table 1.

Example 5

The same procedures used in Example 4 were repeated except that theforegoing APP-3 commercially available was substituted for the APP-2used in Example 4 to thus give 110 parts by weight of thermoplasticresin-coated ammonium polyphosphate particles. The surface of theproduct was observed with an electron microscope and as a result, itcould be confirmed that the ammonium polyphosphate particles wereuniformly coated with the resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was subjected to the foregoing various kinds of qualityevaluation tests. The results thus obtained are summarized in thefollowing Table 1.

Example 6

To a 500 ml volume reactor equipped with a stirrer, a thermometer, arefluxing device and an inlet port, there were added 100 parts by weightof APP-1 prepared above, 7 parts by weight of acrylonitrile, 3 parts byweight of divinylbenzene, 2 parts by weight of potassium persulfate, 200parts by weight of water and 50 parts by weight of methanol, followed bymixing them at ordinary temperature. Then the reaction system was heatedto 80° C. and these ingredients were reacted at that temperature for 6hours. After cooling the reaction solution, it was filtered, washed withwater and then dried to give 110 parts by weight of thermoplasticresin-coated ammonium polyphosphate. The surface of the product wasobserved with an electron microscope and as a result, it could beconfirmed that the ammonium polyphosphate particles were uniformlycoated with the resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was inspected for properties according to the foregoingvarious kinds of quality evaluation tests. The results thus observed aresummarized in the following Table 1.

Example 7

The same procedures used in Example 6 were repeated except that theamount of the acrylonitrile was changed to 3 parts by weight and that 4parts by weight of styrene monomer was additionally added to thus give115 parts by weight of thermoplastic resin-coated ammonium polyphosphateparticles. The surface of the product was observed with an electronmicroscope and as a result, it could be confirmed that the ammoniumpolyphosphate particles were uniformly coated with the resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was subjected to the foregoing various kinds of qualityevaluation tests. The results thus obtained are summarized in thefollowing Table 1.

Example 8

To a 5-liter volume kneader provided with a heating-kneading means,there were introduced 1000 parts by weight of APP-1, 70 parts by weightof styrene monomer, 30 parts by weight of divinyl benzene and 3 parts byweight of potassium persulfate, followed by mixing them at ordinarytemperature. Then the reaction system was heated up to 100° C. andmaintained at that temperature over 8 hours to give 1102 parts by weightof thermoplastic resin-coated ammonium polyphosphate. The surface of theproduct was observed with an electron microscope and as a result, itcould be confirmed that the ammonium polyphosphate particles wereuniformly coated with the resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was subjected to the foregoing various kinds of qualityevaluation tests. The results thus obtained are summarized in thefollowing Table 1.

Comparative Example 1

The melamine-coated ammonium polyphosphate (APP-1) prepared in ReferenceExample 1 was subjected to the foregoing various kinds of evaluationtest without subjecting it to any treatment. The results thus obtainedare summarized in the following Table 1.

Comparative Example 2

The formaldehyde-modified melamine-coated ammonium polyphosphate (APP-2)prepared according to the method used in Reference Example 2 wassubjected to the foregoing various kinds of evaluation test withoutsubjecting it to any treatment. The results thus obtained are summarizedin the following Table 1.

Comparative Example 3

Hostaflam AP462 (APP-3, available from Hoechst Company) was subjected tothe foregoing various kinds of evaluation test without subjecting it toany treatment. The results thus obtained are summarized in the followingTable 1.

Comparative Example 4

To a 500 ml volume reactor equipped with a stirrer, a thermometer, arefluxing device and an inlet port, there were added 100 parts by weightof APP-1, 10 parts by weight of styrene monomer, 2 parts by weight ofpotassium persulfate, 200 parts by weight of water and 50 parts byweight of methanol, followed by mixing them at ordinary temperature.Then the reaction system was heated to 80° C. and these ingredients werereacted at that temperature for 6 hours.

After cooling the reaction solution, it was filtered, washed with waterand then dried to give 110 parts by weight of a product.

Then, the resulting product was inspected for properties according tothe foregoing various kinds of quality evaluation tests. The resultsthus obtained are summarized in the following Table 1.

Comparative Example 5

The same procedures used in Example 1 were repeated except that ammoniumpolyphosphate (110 parts by weight) having the crystalline form II andan average particle size of about 15m was substituted for themelamine-coated ammonium polyphosphate (APP-1), without anypre-treatment to thus obtain thermoplastic resin-coated ammoniumpolyphosphate. The product was observed with an electron microscope andas a result, it was confirmed that the product was uniformly coated withthe resin.

Moreover, the resulting thermoplastic resin-coated ammoniumpolyphosphate was subjected to the foregoing various kinds of qualityevaluation tests. The results thus obtained are summarized in thefollowing Table 1.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Water- 0.3 0.20.1 0.3 0.4 0.4 0.4 0.5 Solubility (%) Resistance to 17.5 16.7 8.4 14.315.0 17.5 16.0 17.1 Acids (%) Resistance to 19.5 19.3 9.1 15.5 15.7 18.017.6 18.7 Alkali (%) Resistance to 11.5 10.9 6.2 9.5 10.1 9.7 9.4 12.4Ions (%) Resistance to Org. Solv. (%) 0 0 0 0 0 0 0 0 Elec. Cond. 0.570.40 0.31 0.35 0.44 0.61 0.65 0.86 (10⁻³/Ω · m) Flame Retard. 30.4 30.830.0 30.5 30.7 31.0 30.4 30.6 (O.I.) Impact Res. 8.1 7.9 8.9 8.3 8.0 7.57.7 7.0 Test (kJ/m²) Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex.4 Ex. 5 Water-Solubility 19.3 0.7 4.2 2.5 56.5 (%) Resistance to Acids40.7 22.8 25.6 27.6 45.9 (%) Resistance to Alkali 58.5 54.1 46.1 60.989.8 (%) Resistance to Ions 31.3 18.9 20.2 19.2 41.6 (%) Resistance toOrg. Solv. (%) 0.02 0 0 8.5 0 Elec. Cond. 120.8 72.1 80.2 17.8 125.7(10⁻³/Ω · m) Flame Retard. 30.1 30.5 30.2 29.8 30.0 (O.I.) Impact Res.Test 4.1 4.5 4.3 5.8 7.0 (kJ/m²) Note: With regard to thewater-solubility, resistance to acids (Res. to Acids), resistance toalkalis (Res. to Alk.), resistance to ions (Res. to ions) and resistanceto organic solvents (Res. to Org. Solv.), the lower the measured value,the more excellent the corresponding property.

What is claimed is:
 1. A thermoplastic resin-coated ammoniumpolyphosphate comprising a core material and a coating layer, whereinsaid core material comprises ammonium polyphosphate and a thermosettingresin, a melamine monomer, or a surface-treating agent; and said coatinglayer comprises a thermoplastic resin.
 2. The thermoplastic resin-coatedammonium polyphosphate as set forth in claim 1 wherein the thermoplasticresin is a member selected from the group consisting of homopolymers ofa monomer represented by the following general formula 1 which has, inthe molecule, 2 to 5 double bonds capable of undergoing polymerization;copolymers of at least two of these monomers represented by the generalformula 1; copolymers of at least one monomer represented by thefollowing general formula 1 with at least one monomer represented by thefollowing general formula 2; and mixtures thereof:

wherein R₁, R₂ and R₃ of formula 1 may be the same or different from oneanother and each represents a member selected from the group consistingof a hydrogen atom, halogen atoms, cyano groups, cyanoalkyl groupshaving 1 to 8 carbon atoms, carboxyl groups, alkyl groups having 1 to 10carbon atoms, alkyl ether groups having 2 to 15 carbon atoms, aminoalkylgroups having 1 to 10 carbon atoms, alkenyl groups having 2 to 12 carbonatoms, alkynyl groups having 2 to 1 2 carbon atoms, alkyl ester groupshaving 2 to 18 carbon atoms and alkoxy groups having 1 to 1 4 carbonatoms, provided that if one of the groups R₁, R₂ and R₃ is a carboxylgroup or an alkyl ester group having 2 to 18 carbon atoms, the othergroups represent groups different from the functional group and R₄represents a group represented by the following general formula 3 or 4;

wherein R₈, R₉, R₁₀ and R₁₁ of formula 2 are the same or different fromeach other and each represents a member selected from the groupconsisting of a hydrogen atom, halogen atoms, cyano groups, cyanoalkylgroups having 1 to 8 carbon atoms, carboxyl groups, alkyl groups having1 to 10 carbon atoms, alkyl ether groups having 2 to 15 carbon atoms,aminoalkyl groups having 1 to 10 carbon atoms, aromatic groups having 6to 32 carbon atoms and alkyl ester groups having 2 to 18 carbon atoms,provided that if one of the groups R₈, R₉, R₁₀ and R₁₁ is a carboxylgroup or an alkyl ester group having 2 to 18 carbon atoms, the othergroups represent groups different from the functional group;

wherein R₁ and R₂ of formula 3 are the same as those defined above inconnection with the general formula 1, respectively and R₅ is a grouprepresented by the following general formula 5, 6, 7 or 8;

wherein R₁, R₂ and R₃ of formula 4 are the same as those defined abovein connection with the general formula 1, respectively;

wherein R₆ and R₇ of formula 5 are the same or different from oneanother and each represents a member selected from the group consistingof a hydrogen atom, halogen atoms, cyano groups, cyanoalkyl groupshaving 1 to 8 carbon atoms, aminoalkyl groups having 1 to 10 carbonatoms, aromatic groups having 6 to 32 carbon atoms and those representedby the foregoing general formula 3 or 4 and p is a numeral ranging from1 to 12;

wherein R₆ and R₇ and p of formula 6 are the same as those defined abovein connection with the formula 5, respectively; —Ar—  7 wherein Ar offormula 7 represents an aromatic residue having 6 to 32 carbon atoms;

wherein R₄ of formula 8 is the same as that defined above in connectionwith the general formula
 3. 3. The thermoplastic resin-coated ammoniumpolyphosphate as set forth in claim 2 wherein the monomer represented bythe general formula 1 is a conjugated diene monomer or a non-conjugateddiene monomer, which has two polymerizable double bonds.
 4. Thethermoplastic resin-coated ammonium polyphosphate as set forth in claim2 wherein the thermoplastic resin is used in an amount ranging from 1 to40 parts by weight per 100 parts by weight of the core material.
 5. Thethermoplastic resin-coated ammonium polyphosphate as set forth in claim2, wherein the core material is ammonium polyphosphate covered orencapsulated in a thermosetting resin.
 6. The thermoplastic resin-coatedammonium polyphosphate as set forth in claim 2, wherein the corematerial is ammonium polyphosphate covered or modified with a melaminemonomer.
 7. The thermoplastic resin-coated ammonium polyphosphate as setforth in claim 2, wherein the core material is surface-treated ammoniumpolyphosphate obtained by adhering, adsorbing or absorbing asurface-treating agent on or to the surface of ammonium polyphosphate.8. The thermoplastic resin-coated ammonium polyphosphate as set forth inclaim 1 wherein the thermoplastic resin is used in an amount rangingfrom 1 to 40 parts by weight per 100 parts by weight of the corematerial.
 9. The thermoplastic resin-coated ammonium polyphosphate asset forth in claim 8 wherein the monomer represented by the generalformula 1 is a conjugated diene monomer or a non-conjugated dienemonomer, which has two polymerizable double bonds.
 10. The thermoplasticresin-coated ammonium polyphosphate as set forth in claim 1 wherein thecore material is ammonium polyphosphate covered with or encapsulated ina thermosetting resin.
 11. The thermoplastic resin-coated ammoniumpolyphosphate as set forth in claim 10 wherein the thermosetting resinis at least one member selected from the group consisting of melamineresins, modified melamine resins, guanamine resins, epoxy resins,phenolic resins, urethane resins, urea resins and silicone resins. 12.The thermoplastic resin-coated ammonium polyphosphate as set forth inclaim 10 wherein the surface-treating agent is at least one memberselected from the group consisting of saturated or unsaturated fattyacids having 6 to 25 carbon atoms, metal salts of saturated orunsaturated fatty acids having 6 to 25 carbon atoms, silane couplingagents, titanate coupling agents, aluminate coupling agents, anionicsurfactants, cationic surfactants, nonionic surfactants, amphotericsurfactants and fluorine atom-containing surfactants.
 13. Thethermoplastic resin-coated ammonium polyphosphate as set forth in claim10 wherein the ammonium polyphosphate has a phosphorus atomconcentration ranging from 20 to 31% by weight.
 14. The thermoplasticresin-coated ammonium polyphosphate as set forth in claim 1 wherein thecore material is ammonium polyphosphate covered or modified with amelamine monomer.
 15. The thermoplastic resin-coated ammoniumpolyphosphate as set forth in claim 1 wherein the core material issurface-treated ammonium polyphosphate obtained by adhering, adsorbingor absorbing a surface-treating agent on or to the surface of ammoniumpolyphosphate.
 16. The thermoplastic resin-coated ammonium polyphosphateas set forth in claim 1 wherein it has an average particle size rangingfrom 0.1 to 50 μm.
 17. A flame retardant comprising, as an effectivecomponent, the thermoplastic resin-coated ammonium polyphosphate as setforth in claim
 1. 18. A process for producing thermoplastic resin-coatedammonium polyphosphate comprising the step of subjecting, to apolymerization reaction, a monomer represented by the general formula 1and a monomer represented by the general formula 2 as an optionalcomponent, in the presence of a catalyst, in the presence or absence ofa reaction solvent, on the surface of a core material which comprisesammonium polyphosphate and a thermosetting resin, a melamine monomer ora surface-treating agent.
 19. The process for producing thermoplasticresin-coated ammonium polyphosphate as set forth in claim 18 wherein thetemperature for the polymerization of the monomers ranges from 20 to150° C.
 20. The process for producing thermoplastic resin-coatedammonium polyphosphate as set forth in claim 19 wherein it comprises thesteps of introducing, into a reactor, the core material, and 0.1 to 40parts by weight of the monomer of the formula 1, 0.1 to 39.9 parts byweight of the monomer of the formula 2, 0.1 to 10 parts by weight of thecatalyst, per 100 parts by weight of the core material, and a reactionsolvent and then reacting the monomers at a temperature ranging from 20to 150° C. for 0.5 to 50 hours.
 21. The process for producingthermoplastic resin-coated ammonium polyphosphate as set forth in claim18 wherein it comprises the steps of introducing, into a reactor, thecore material, and 0.1 to 40 parts by weight of the monomer of theformula 1, 0.1 to 39.9 parts by weight of the monomer of the formula 2,0.1 to 10 parts by weight of the catalyst, per 100 parts by weight ofthe core material, and a reaction solvent and then reacting the monomersat a temperature ranging from 20 to 150° C. for 0.5 to 50 hours.